The most common disk images are ISO files, with extension .iso
Under Linux/Mac OS X, the following command can be used to mount the ISO image to the directory /mnt/iso
mount -o loop -t iso9660 filename.iso /mnt/iso
Windows doesn’t natively support disk images, so you’ll need a third-party software. I strongly recommend the FREE DaemonTools. It is light-weight (<500KB) but very powerful. It supports cue/bin, iso, ccd (CloneCD), bwt(Blindwrite), mds (Media Descriptor File), cdi (Discjuggler), nrg (Nero), pdi (Instant CD/DVD), b5t (BlindWrite 5).